Alignment mark, alignment apparatus and method, exposure apparatus, and device manufacturing method

ABSTRACT

An alignment mark includes a first mark usable for global alignment measurement in the direction of a scribe line, and a second mark usable for pre-alignment measurement in a direction perpendicular to the direction of the scribe line. The first mark is formed by arranging a plurality of strip-shaped X measurement marks whose longitudinal direction is perpendicular to the direction of the scribe line. In the second mark, strip-shaped second measurement marks are arranged at the two ends of the first mark such that the longitudinal direction of the second measurement mark is perpendicular to that of the first measurement mark. The alignment mark can be shared by global alignment and pre-alignment, and applied to a narrow scribe line.

This application is a divisional application of U.S. patent applicationSer. No. 10/241,534, filed Sep. 12, 2002 now U.S. Pat. No. 7,006,225.

FIELD OF THE INVENTION

The present invention relates to alignment marks and a substrate withthe alignment marks, a positioning apparatus and method, an exposureapparatus using the positioning apparatus, and a device manufacturingmethod, provided in exposure processing and the like performed by asemiconductor exposure apparatus.

BACKGROUND OF THE INVENTION

Wafer alignment in a general semiconductor manufacturing apparatus willbe described with reference to FIGS. 11, 12, and 13. If a wafer W issupplied to the semiconductor manufacturing apparatus, first, mechanicalpre-alignment is performed in step S01. A mechanical alignment apparatusMA mechanically aligns the wafer W by using the periphery of the wafer Wand an orientation flat or notch (notch N is shown in FIG. 12) formed onthe periphery of the wafer to determine the rough position of the waferW. The mechanical alignment precision is about 20 μm.

In step S02, the wafer W is set on a chuck CH and supplied to a stageSTG by a wafer supply apparatus (not shown), and pre-aligned in stepS03. In pre-alignment, a mirror MM is inserted into an optical path in ascope SC (the mirror MM moves to the right in FIG. 13). Light from analignment mark illumination light source Li is detected by a sensor S1set to a low magnification. Left and right pre-alignment marks (PAL andPAR) shown in FIG. 12 are detected using the low-magnification sensorS1, and their mark positions are obtained to attain the center of thewafer. The alignment precision in this pre-alignment is about 4 μm.

Then, global alignment is performed to accurately obtain the position ofthe wafer W and the position of an exposure shot in step S04. In globalalignment, the mirror MM is removed from the optical path (the mirror MMmoves to the left in FIG. 13). A sensor S2 set to a high magnificationis used to measure the positions of a plurality of global alignmentmarks (FX1 to FX4 and FY1 to FY4) on the wafer W shown in FIG. 12. Inthis manner, X- and Y-direction shifts of the wafer W, the rotationalcomponent, and the magnification component of the shot array areobtained. The global alignment precision must be 50 nm or less in amachine which manufactures current 256-Mbit memories. After globalalignment ends, exposure starts in step S05.

As described above, accurately obtaining the wafer position requires atleast pre-alignment and global alignment on the chuck CH. Furthermore,since pre-alignment and global alignment have different detectiontargets, two kinds of marks are required.

In pre-alignment, the mark must be detected in a wide field of viewafter mechanical rough alignment. The mark must be detected by alow-magnification scope and must be as large as about 100 μm. In globalalignment, the mark is precisely detected by a high-magnification scopebecause the mark has already been aligned with a shift of about 4 μm bypre-alignment. Hence, the marks are small.

In recent semiconductor fabrication, the wafer processing called CMP(Chemical Mechanical Polish) is mainly performed. An alignment mark on awafer having undergone the CMP must be accurately measured. Hence, theshape and line width of the alignment mark must be tuned in accordancewith the processing. Both the pre-alignment mark and global alignmentmark must be respectively tuned. Tuning of the two kinds of marksrequires a long time, and decreases the yield.

Recently, in order to minimize the manufacturing cost of thesemiconductor, a scribe line in which the alignment mark and the likecan be arranged is narrowed. In some cases, a scribe line with a widthequal to or smaller than the size of the pre-alignment mark is required.

Additionally, in the step of forming a bonding pad, since the steps of ascribe line become large, the size of the alignment mark is furtherstrictly limited. FIGS. 14A to 14D show the scribe line, a pre-alignmentmark PA, and a global alignment mark F. Reference numerals s11 and s12in FIG. 14A denote edges of the scribe line, and an interval between theedges is the width of the scribe line. When the steps of the scribe lineare small as shown in FIG. 14B, no problem arises in the relationshipbetween the width of the scribe line and the size of the alignment marksshown in FIG. 14A.

However, in the step of forming the bonding pad, the steps of the scribeline become large, and a resist is applied to these large steps. Hence,unobservable areas are increased, and the areas in which thepre-alignment marks can be accurately observed are further narrowed.Hence, the pre-alignment marks of 100 μm are difficult to detect. FIGS.14C and 14D show this state. When the steps of the edge portions s11 ands12 become large and a resist R is applied to the steps, the resistthickness sharply changes at the edge portions. When the change portionsare observed with a scope SC shown in FIG. 13, the intensity ofscattered light on the resist change portions is increased, and theareas of DA1 and DA2 in FIG. 14C cannot be observed by dark fieldillumination. As a consequence, the edges of the pre-alignment mark PAcannot be observed. When bright field illumination is used, light in theresist change portions is also scattered and the intensity of reflectedlight is decreased. Therefore, in an image observed by the scope SC, theareas DA1 and DA2 shown in FIG. 14C cannot be observed, and thus theedges of the pre-alignment mark PA become black and cannot be observed.

While the detection of the marks becomes difficult, demands are arisingfor short-time detection and measurement. Since the number of wafersprocessed per unit time must be increased, the time of processing calledalignment not accompanied by exposure must be shortened as much aspossible.

As described above, in general alignment, the following problems arise.

(1) Two kinds of marks are required for wafer alignment.

(2) Since the scribe line becomes narrow, or the observable area becomesnarrow, a large pre-alignment mark cannot be arranged in the scribeline.

(3) Alignment processing time is required to be shortened.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of the abovesituation, and has as its object to provide alignment marks which can beshared by global alignment and pre-alignment and applied to a narrowscribe line, an alignment apparatus which uses the alignment marks, amethod thereof, and the like.

It is another object of the present invention to provide an alignmentapparatus which is effective in performing alignment using the alignmentmarks which can be shared by global alignment and pre-alignment, and canreduce the alignment processing time, a method thereof, and the like.

According to the present invention, the foregoing object is attained byproviding an alignment mark, comprising a first mark usable for globalalignment measurement in a first direction, and a second mark usable forpre-alignment measurement in a second direction.

According to the present invention, the foregoing object is attained byproviding an alignment apparatus which positions a substrate having analignment mark, comprising first measurement means for detecting thealignment mark on the substrate at a first magnification, and secondmeasurement means for detecting the alignment mark on the substrate at asecond magnification higher than the first magnification, wherein thefirst measurement means and the second measurement means share anobjective unit, and a mark detection system is arranged so that thealignment mark can be detected at the first and second magnificationswithout switching an optical path.

According to the present invention, the foregoing object is attained byproviding an alignment apparatus which positions a substrate having analignment mark which includes a first mark usable for global alignmentmeasurement in a first direction, and a second mark usable forpre-alignment measurement in a second direction, comprising firstmeasurement means for performing pre-alignment measurement in the firstand second directions of the alignment mark by using the first mark andthe second mark, moving means for moving to correct a position of thesubstrate on the basis of a result of the pre-alignment measurement, andsecond measurement means for performing global alignment measurement bythe first mark in the first direction of the alignment mark by using thefirst mark after moving the substrate.

According to the present invention, the foregoing object is attained byproviding an alignment method of positioning a substrate having analignment mark including a first mark usable for global alignmentmeasurement in a first direction and a second mark usable forpre-alignment measurement in a second direction, comprising the firstmeasurement step of performing the pre-alignment measurement in thefirst and second directions of the alignment mark by using the first andsecond marks, the moving step of moving the substrate to correct theposition on the basis of a result of the pre-alignment measurement, andthe second measurement step of performing the global alignmentmeasurement in the first direction of the alignment mark by using thefirst mark after the moving step.

According to the present invention, the foregoing object is attained byproviding an alignment method of positioning a substrate havingalignment marks, comprising the first measurement step of detecting thealignment mark on the substrate at a first magnification, and the secondmeasurement step of detecting the alignment mark on the substrate at asecond magnification higher than the first magnification, wherein in thefirst and second measurement steps, the alignment mark is detected usingmark detection systems which share an objective unit and detect atrespective magnifications by branching an optical path without switchingthe optical path.

According to the present invention, the foregoing object is attained byproviding a substrate having an alignment mark on a scribe line, whereinthe alignment mark comprises a first mark usable for global alignmentmeasurement in a first direction which is a direction along which thescribe line extends, and a second mark usable for pre-alignmentmeasurement in a second direction perpendicular to the first direction.

Also, according to another aspect of the present invention, an exposureapparatus and a device manufacturing method using the above alignmentapparatus are provided.

Other features and advantages of the present invention will be apparentfrom the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

FIGS. 1A and 1B are views showing alignment marks in the firstembodiment;

FIG. 2 is a view showing the example of a template used for detectingthe alignment mark shown in FIG. 1A by image processing;

FIG. 3 is a view showing a state in which a window for high-presitionmeasurement is set for the alignment mark in FIG. 1A;

FIGS. 4A and 4B are views for explaining a barycenter calculation by thewindow for high-precision meausrement;

FIG. 5 is a flow chart for explaining pre-alignment processing in thefirst embodiment;

FIGS. 6A and 6B are views showing another example of the alignment markswhich can be shared by global alignment and pre-alignment, and arrangedin a narrow scribe line;

FIG. 7 is a view showing a state in which the alignment marks in FIG. 6Aare arranged in vertical and horizontal scribe lines on the wafer;

FIG. 8 is a view showing the arrangement of an exposure apparatus in thefourth embodiment;

FIG. 9 is a flow chart for explaining alignment processing in the fourthembodiment;

FIG. 10 is a flow chart for explaining the procedure of alignment markmeasurement in the fourth embodiment;

FIG. 11 is a flow chart for explaining the procedure of generalalignment processing;

FIG. 12 is a view showing alignment marks on a general wafer;

FIG. 13 is a view for explaining the alignment mechanism of a generalexposure apparatus;

FIGS. 14A to 14D are views showing scribe lines, pre-alignment marks AP,and global alignment marks F;

FIG. 15 is a view showing the flow of the entire manufacturing processof a semiconductor device; and

FIG. 16 is a view showing the detailed flow of the wafer process shownin FIG. 15.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will be described indetail in accordance with the accompanying drawings.

(First Embodiment)

FIGS. 1A and 1B show alignment marks in the first embodiment. Each ofthe marks shown in FIGS. 1A and 1B can be arranged in a narrow scribeline. The marks can measure both X and Y directions at high precision,and be shared by global alignment and pre-alignment.

As shown in FIG. 1A, strip-shaped first measurement marks X1, X2, X3,and X4 are arranged in a direction along which each scribe line extends.The longitudinal direction of each of the marks is perpendicular to thedirection of the scribe line. The first measurement marks X1 to X4 arerarely influenced by the scribe line because the marks are less affectedby the scribe line in windows for high-precision detection (to bedescribed later). Second measurement marks Y1 and Y2 are arrangedoutside the first measurement marks X1 to X4. The longitudinal directionof each of the marks is along the direction of the scribe line. Thesecond measurement marks Y1 and Y2 are arranged at the center of thescribe line in order to minimize the influence of the scribe line. Notethat, in FIG. 1A, the scribe line extends from left to right, and thedirection of the scribe line coincides with the X direction. The firstmeasurement marks (X1 to X4) and the second measurement marks (Y1, Y2)are called X measurement marks and Y measurement marks, respectively.

The position of the alignment mark shown in FIG. 1A is obtained bytemplate matching done by image processing. FIG. 2 is a view showing theexample of a template used for detecting the alignment mark in FIG. 1Aby the image processing. In this case, the mark is illuminated with adark field illumination system, a received image is binarized, and themark position is searched by pattern matching. Because of the dark fieldillumination, the outline of the mark has high luminance (white), and aportion having no pattern has low luminance (black). Therefore, when theimage is binarized, the outline becomes white (1), and the remainingportions become black (0).

As shown in FIG. 2, the template for template matching has a pattern inwhich the outline of the mark is white and the background of the mark isblack. If the number of white patterns equals that of the blackpatterns, a high detection rate can be obtained. This is because whenthe template has many white patterns in binarizing the image includingthe mark, the white area is increased in the binarized image, therebyincreasing the degree of correlation. On the other hand, when thetemplate has many black patterns, the degree of correlation decreases.In this manner, regardless of the shape of the mark, the detection rateis influenced when the degree of correlation is changed by areflectance. Note that an indeterminate portion (portion indeterminatefor a white or black portion) and a portion useless as templateinformation have no template information, and are excluded from thetarget of the matching processing.

The feature of the template pattern shown in FIG. 2 is that there arefour vertical lines, two horizontal lines, and five blank portionsbetween the vertical lines and between the vertical and horizontallines. Blank portions are also formed at the left and right of the endportions of the horizontal lines. The detection rate of pattern matchingcan be increased by arranging the features of the marks and atwo-dimensional pattern on the template. When damage caused by the stepsnear the edges of the scribe line can be expected in the observablearea, the template information is not included in this area. Thetemplate information is included only in an area with no damage. In anexample in FIG. 2, each of the end portions of the X measurement marksX1, X2, X3, and X4 and the Y measurement marks Y1 and Y2 does not haveany template information. The end portions of the X measurement marksare excluded from the target of the matching processing because theinfluence caused by the steps of the edges of the scribe line must beeliminated. This is because, for example, when areas DA1 and DA2 in FIG.14C are increased upon arranging the marks shown in FIG. 1A in thescribe line as shown in FIG. 14C, the end portions of the marks X1, X2,X3, and X4 are readily influenced.

In pattern matching by the template as described above, the markpositions can be detected in the precision of one or two pixels.However, in pre-alignment measurement for implementing global alignmentmeasurement, the mark positions must be obtained at higher resolvingpower, i.e., in the precision of one pixel or less. A method ofobtaining the mark positions in the precision of one pixel or less willbe described below.

When the mark positions are determined in precision of one or two pixelsby pattern matching described above, on the basis of the determinedpositions, windows for high-precision measurement are set in theportions determined by the set values of the marks. FIG. 3 is a viewshowing a state in which the windows for high-precision measurement arearranged for the alignment mark in FIG. 1A. Then, the information of theposition is compressed to a one-dimensional signal by projectionprocessing in a mark non-measuring direction in each of the windows WX1,WX2, WX3, WX4, WY1, and WY2. Processing represented by a barycentercalculation is performed for the compressed signal to calculate thepositions of the measurement marks in precision of one pixel or less.For example, as shown in FIG. 4A, the window WX1 for high-precisionmeasurement is set for the X measurement mark X1. Then, as shown in FIG.4B, the X measurement mark X1 is projected in the non-measuringdirection (the Y direction) in this window WX1, thereby obtaining abarycenter X1G.

In this manner, the average of the positions of all the X measurementmarks in the X direction and the average of the positions of all the Ymeasurement marks in the Y direction are calculated in one alignmentmark. The average values are used as measurement results obtained bypre-alignment performed for the alignment marks in the X and Ycoordinates. As described above, the marks are detected by templatematching at a low magnification. The marks are detected by a barycentercalculation after the windows are set, projected, and integrated at ahigh magnification.

The above pre-alignment processing will be further described withreference to FIG. 5. Note that an exposure apparatus for performingpre-alignment processing in this embodiment is the same as the exposureapparatus shown in FIG. 13. FIG. 5 is a flow chart for explaining thepre-alignment processing in the first embodiment. The flow chart in FIG.5 describes the pre-alignment processing performed by the scope SC afterthe wafer having undergone mechanical alignment by the mechanicalalignment apparatus MA is set on the chuck, and the chuck with the waferis set on the stage STG.

First, in step S11, the position of the alignment mark in FIG. 1A ismeasured by using the template shown in FIG. 2. In step S12, theposition of the wafer is corrected on the basis of the measurementresult. In step S13, the windows for high-precision measurement as shownin FIG. 3A are set. In step S14, the marks are projected in the setwindows for high-precision measurement, and the barycenter positions arecalculated to determine the position of the alignment mark (FIG. 3B).With the processing described above, the pre-alignment measurement usingthe mark in FIG. 1A can be performed, and the measurement result isoutput in step S15. For example, the global alignment measurement can beperformed by using this measurement result. Note that the entireprocedure of the alignment processing including the global alignmentmeasurement will be described in detail in the third and fourthembodiments.

Note that the alignment mark in FIG. 1B is used for preventing adetection error in pre-alignment. As shown in FIG. 1B, two differentintervals d1 and d2 are formed between the X measurement marks. Themarks can have more characteristic patterns by changing the width of theintervals between the X measurement marks. That is, even if the wiringpattern with an interval d is detected, wiring patterns with theintervals d1 and d2 hardly exist at the same time. Hence, the mark inFIG. 1B can more prevent the detection error than that in FIG. 1A. Alsoin FIG. 1B, the windows for high-precision measurement similar to thatin FIG. 3A are set for the X and Y measurement marks, the information iscompressed by the projection processing as described in FIG. 3B, and thebarycenter is calculated. Hence, the mark position is obtained in theprecision of one pixel or less.

Note that the alignment marks in FIGS. 1A and 1B show the marks whichcan be arranged in horizontal scribe lines (the scribe lines arranged inthe direction which coincides with the X direction). If the marks arerotated through 90°, the alignment marks show the marks which can bearranged in vertical scribe lines (the scribe lines arranged in thedirection which coincides with the Y direction). The marks, template,and processes are the same as described above. That is, when the marksare arranged in the vertical scribe lines, the measurement marks X1 toX4 serve as the Y measurement marks, and the measurement marks Y1 and Y2serve as the X measurement marks.

In the first embodiment, the pattern obtained by the dark fieldillumination is binarized, the mark positions are detected by patternmatching, and the mark positions are obtained by a barycentercalculation with a high resolution. However, as long as the marks can beidentified, the bright field illumination or other illumination can beused. When the bright field illumination is used, the outline of thepattern may be black. Hence, white and black portions of the templateshown in FIG. 2 may be inverted.

A method of obtaining mark positions is not limited to the binarization.For example, various methods, e.g., a method of extracting the outlineof the marks and performing pattern matching can be applied.

(Second Embodiment)

FIGS. 6A and 6B show another example of alignment marks each of whichcan be shared by global alignment and pre-alignment, and arranged in anarrow scribe line.

The alignment mark shown in FIG. 6A is so designed as to reduce theinfluence of a resist applied onto a mark on detection. Two fence marks(401 and 402) are arranged outside four center X marks. A plurality ofmarks including these fence marks smooth nonuniformity of a resistportion to reduce the resist coating nonuniformity. In FIG. 6B, thefence marks 401 and 402 which reduce the influence of resist coating arearranged. In addition, the interval between the four center measurementmarks is changed to decrease the erroneous detection frequency inpre-alignment, similar to the alignment mark of FIG. 1B.

Note that the procedure of pre-alignment measurement for the alignmentmarks shown in FIGS. 6A and 6B is the same as that described in thefirst embodiment (FIG. 5).

As described above, the following effects can be obtained by thealignment marks in the first and second embodiments. That is,

-   1. The alignment marks which can be arranged in the scribe lines and    measure the X and Y coordinates at high precision can be obtained.-   2. The global alignment mark (X measurement marks in FIGS. 1A and 1B    and FIGS. 6A and 6B) in which an auxiliary pattern (Y measurement    marks in FIGS. 1A and 1B and FIGS. 6A and 6B) is added is employed.    Hence, the alignment marks which can be shared by pre-alignment and    global alignment can be provided.-   3. Since the auxiliary pattern is arranged at the center of the    scribe line, the pattern is not affected by the edges of the scribe    line in the measurement direction.-   4. The mark for measuring both pre-alignment and global alignment is    used. Hence, the size of the pre-alignment mark is reduced, and the    damage, e.g., narrowed observable area can be prevented.    Additionally, a mark dedicated area can be narrowed.-   5. In mark tuning such as CMP, both pre-alignment and global    alignment need not be tuned, thereby increasing the yield and    productivity.    (Third Embodiment)

In the third embodiment, alignment processing including global alignmentwill be described by using the alignment marks described in the firstand second embodiments and pre-alignment measurement thereof. In globalalignment using the alignment marks described in FIGS. 1A and 1B andFIGS. 6A and 6B, the X measurement marks X1 to X4 are observed by thehigh-magnification scope, and the positions of the X alignment marks aredetected at higher resolving power than in pre-alignment by the methoddescribed in FIGS. 3 and 4. A procedure will be described with referenceto the alignment mark in FIG. 6A, but alignment can be performed in thesame procedure using the alignment marks in FIG. 6B and FIGS. 1A and 1B.

FIG. 7 shows a state in which the alignment marks shown in FIG. 6A arearranged in vertical and horizontal scribe lines on the wafer. Thealignment marks shown in FIG. 6A are arranged in the horizontal scribelines (FX1 to FX4), and used for the X measurement in global alignment.The marks shown in FIG. 6A rotated through 90° are arranged in thevertical scribe lines (FY1 to FY4), and used for the Y measurement inglobal alignment.

With reference to FIGS. 7, 11, and 13, alignment processing by using themarks which can be shared by global alignment and pre-alignment will bedescribed below. If a wafer W is supplied to a semiconductormanufacturing apparatus, a mechanical alignment apparatus MAmechanically aligns the wafer W by using the periphery of the wafer anda notch N to determine the rough position of the wafer W (step S01).Then, the wafer is set on a chuck CH by a wafer supply apparatus (notshown) (step S02), supplied to a stage STG, and pre-aligned (step S03).In pre-alignment, a mirror MM moves to the right in FIG. 13. The X and Ypositions of the alignment marks FX1 and FX3 or FY1 and FY3 shown inFIG. 7 are sensed using the low-magnification sensor S1 of a scope SC todetect the center of the wafer. At this time, the pre-alignmentmeasurement is performed in the procedure shown in step S11 in FIG. 5.The pre-alignment precision is higher as the interval between two marksto be measured is larger.

On the basis of the center of the wafer obtained by the abovepre-alignment, global alignment is performed to accurately obtain thewafer position and exposure shot position (step S04). Then, exposurestarts (step S05). In global alignment, measurement is performed in theprocedure shown in steps S13 to S15 in FIG. 5. Note that globalalignment is performed by moving the mirror MM in the scope SC to theleft in FIG. 13, and using a high-magnification sensor S2. In globalalignment, each of the X measurement marks in the plurality of alignmentmarks FX1 to FX4 and each of the Y measurement marks in the alignmentmarks FY1 to FY4 on the wafer are measured. In this manner, X- andY-direction shifts of the wafer W, the rotational component, and themagnification component of the shot array, are obtained.

Note that in the above alignment processing, pre-alignment is performedusing FX1 and FX3 (or FY1 and FY3), and after that, global alignment isperformed using FX1 to FX4, and FY1 to FY4. However, the globalalignment measurement may be performed for the marks immediately aftereach of pre-alignment measurement for FX1 and FX3 (or FY1 and FY3). Inthis manner, the moving amount of the stage STG for performing thepre-alignment measurement and the global alignment measurement for FX1and FX3 (or FY1 and FY3) can be reduced.

In global alignment using the high-magnification sensor for detectingthe positions of the alignment marks, the erroneous detection frequencybecomes low with a change in measurement mark interval even at oneportion in detecting a mark position (FIGS. 1B and 6B) as compared withthe same interval between the X measurement marks (FIGS. 1A and 6A). Thereason for this is as follows. When four mark positions on the markshown in FIG. 6B are accurately obtained, the interval between marks maybe erroneously detected as a mark. This occurs when a pseudo markappears between marks due to generation of interference fringes. Bychanging even one interval between measurement marks, the mark intervalis compared with the mark design value after detection of four markpositions, and whether the mark is erroneously detected can be checked.A retry function of, if erroneous detection is determined, changing thetarget processing position to a position shifted by half the pitch andcalculating the position again can be added.

(Fourth Embodiment)

In the above third embodiment, when the positions of the alignment marksshown in FIGS. 1A and 1B and FIGS. 6A and 6B are to be detected, thepre-alignment measurement is performed by the low-magnification scopeSC, and then the global alignment measurement is performed by switchingthe scope SC to a high magnification. In the fourth embodiment, thescope can simultaneously observe the marks at low and highmagnifications, a mirror need not be switched, and a wafer alignmenttime can be further reduced.

FIG. 8 shows the arrangement of an exposure apparatus in the fourthembodiment. In this arrangement, the scope SC for wafer alignment shownin FIG. 8 can simultaneously observe low- and high-magnification imagesby sharing an objective unit. Hence, the mark positions can be detectedwithout switching, e.g., moving a mirror MM. Illumination light isguided from an alignment mark illumination light source Li into thescope SC, and illuminates the marks on the wafer through a half-mirrorM1. For example, the light illuminates the mark FX1 in FIG.7. Lightreflected by a wafer W reaches a high-magnification sensor 32 andlow-magnification sensor S1 through the half-mirror M1 and a half-mirrorM2. Image signals sensed by the sensors S1 and S2 are processed by analignment mark measurement processing apparatus P to measure thepositions of the alignment marks.

A main controller MC controls a driving unit MS which drives a stage STGon the basis of a measurement result from the alignment mark measurementprocessing apparatus P and a signal from a stage position sensor LP. Themain controller MC implements the control of alignment and exposure tobe described below.

Referring to FIGS. 9 and 10, the procedure of detecting the alignmentmarks in the fourth embodiment will be described. After mechanicalalignment performed by a mechanical alignment apparatus MA (step S21)ends, global alignment in the procedure shown in FIG. 10 is performed(step S23) for the wafer W placed on a chuck CH (step S22). In thismanner, when the wafer has been positioned, the exposure starts toexpose a pattern on a mask (MASK) to the wafer W by a projection opticalsystem LENS (step S24).

In global alignment of this embodiment, the wafer moves to the markposition FX1 (step S 101), and the scope SC simultaneously observes themarks by the low- and high-magnification sensors. That is, first, thepositions of the alignment marks are obtained by sensing the mark FX1 ata low magnification (step S102). By using this result, a shift dx1 inthe X direction and a shift dy1 in the Y direction from the target markposition are calculated (step S103). Note that, in low-magnificationmeasurement processing such as step S102, the procedure of thepre-alignment measurement described in step S11 in FIG. 5 is used. Theposition of the wafer W is shifted by the calculated shifts dx1 and dy1so that the wafer W falls within the field of view of thehigh-magnification sensor (step S104). In this state, since the waferfalls within the field of view of the high-magnification sensor, themark FX1 is measured at a high magnification (steps S13 and S14 in FIG.5) using a signal from the senor S2 (step S105).

Next, when the scope is to move to the mark position FY1, the targetmark position FY1 is corrected by the shifts dx1 and dy1 calculated instep S103, then moves to the mark position FY1 (step S106). Since thedistance between the marks FX1 and FY1 is small, the mark FY1 can fallwithin the high-magnification field of view while rarely receiving theinfluence of a θ component obtained upon placing the wafer on the chuck.Therefore, the position measurement processing is immediately performedfor the mark FY1 by the high-magnification sensor S2 (step S107), andthen the scope moves to the position of the next mark FX2.

The positions of the alignment marks FX2 and FY2 are calculated by thesame processes as those in steps S101 to S107 (steps S108 to S114).After two pairs of mark positions ((FX1, FY1) and (FX2, FY2)) arecalculated, the θ component and the shift, i.e., shift X and shift Y ofthe center upon setting the wafer on the chuck can be determined (stepS115). The target positions of the alignment marks FX3, FX4, FY3, andFY4 which have not undergone global alignment measurement are correctedby θ, shift X, and shift Y. That is, the same processes are sequentiallyexecuted for the alignment marks FX3, FY3, FX4, and FY4 by thehigh-magnification detection system. These alignment marks need not beobserved at a low magnification because their target positions areaccurately corrected (steps S116 to S119).

This method can process the wafer without moving the scope SC to PAL andPAR, unlike the prior art which moves the scope SC to the positions PALand PAR to obtain the mark positions. In the measurement of the marksFX1 and FX2, the pre-alignment measurement and the global alignmentmeasurement can be performed without moving the scope SC. This methodcan shorten the stage moving distance (times), and the stage moving timein alignment processing.

Whether the alignment marks have fallen within the field of view of thehigh-magnification sensor is determined on the basis of the shift amount(e.g., dx1, dy1, dx2, and dy2) obtained as a result of thelow-magnification measurement processing. When the marks fall within thefield of view of the high-magnification sensor, the movement by thecalculated shift amount can be omitted. In this manner, an increase inprocessing speed can be further expected.

The arrangement shown in FIG. 8 has been described by exemplifying anoff-axis alignment semiconductor manufacturing apparatus. Thisarrangement can be applied to any type such as the TTL alignment type inwhich the wafer mark is observed through an exposure projection opticalsystem or the TTR alignment type in which a wafer mark is observedthrough a reticle (mask) as far as a scope capable of observing a marksimultaneously at low and high magnifications is used and the mark canbe shared by pre-alignment and global alignment. The above processingcan be implemented by a scope whose magnification is changed by movingthe mirror as shown in FIG. 13.

Note that, in sequential image sensing by the low- andhigh-magnification sensors, the amount of illumination light may bechanged (by ND filter switching and the like) in synchronism with animage sensing sequence so that illumination properly light-controlled isperformed on a sensor. In this case, e.g., during image sensing at a lowmagnification, or before this sensing step, illumination information ofthe wafer may be obtained by sensing image at a low magnification, andlight control using the high-magnification sensor may be performed onthe basis of the information.

Note that after the sequential control for predetermined marks or apredetermined wafer is performed on the basis of the above flow ofalignment, at least a part of the sequence for next marks or wafer maybe omitted. For example, in processing shown in the flow chart in FIG.10, when a plurality of marks are to be detected in global alignment,only the first and second marks are sensed at the low-magnification, andthe third and subsequent marks are directly measured at a highmagnification. The present invention is not limited to this. The θcomponent may be added to the target position data of the measurementmarks to omit θ adjustment processing on the wafer. Alternatively, thesecond and subsequent wafers may be directly measured at a highmagnification by using the low-magnification sensing information of thefirst wafer.

With regard to an image sensing system, NAs (numerical appartures) maybe made different by the optical system in the optical path afterseparating by the half-mirror, and the depth of focus oflow-magnification image sensing may be larger than that ofhigh-magnification image sensing. The wavelengths of the high- andlow-magnification illumination light beams may be made differentdepending on the sensors.

For shortening a time, detection of the marks in the low-magnificationimage sensing, or focusing operation for the low-magnification imagesensing may be started during wafer movement by the stage to theposition for sensing image at a low magnification.

The detection mode of a mark detection system at a high magnificationmay be different from that at a low magnification. For example, thescheme for image processing can be changed in accordance with themagnification. Low-magnification alignment can be performed under thebright field illumination, and high-magnification alignment can bepreformed under the dark field illumination. The mark can be detected bythe reflected light or scattered light in beam scanning in place ofimage sensing.

As described above, according to the above embodiments, pre-alignmentand global alignment can be simultaneously performed. Hence, the stagemoving amount for pre-alignment can be reduced, and alignment can beperformed within a short time.

As described above, according to each embodiment described above, thealignment marks used for both pre-alignment and global alignment areprovided. Hence, the pre-alignment marks become small to cope withdamage such as a narrow observable area. Additionally, the markdedicated area can be made narrow. In mark tuning processing such asCMP, both pre-alignment and global alignment need not be tuned. As aresult, the yield and productivity increase.

Additionally, since the alignment marks are simultaneously observed atthe low and high magnifications, the conventional pre-alignmentprocessing is performed within a short time, and the number of wafers tobe processed per unit time is increased.

Additionally, according to the embodiments, the marks become as small asthe width of the scribe lines, and the marks maintain a size largeenough to be searched at a low magnification in the longitudinaldirection of the scribe line. Hence, the marks, which can cope with thedecrease in width of the scribe line, and can be shared by globalalignment and pre-alignment, are proposed. The marks cannot only copewith the decrease in width of the scribe line, but also decrease theload of tuning the marks by sharing between pre-alignment and finealignment. The detection error can be effectively prevented by differentintervals between the marks and template design in pre-alignment. In theembodiment, since the number of times of stage movement for thepre-alignment processing and the moving amount are reduced, thethroughput is increased. The marks of the present invention caneffectively increase the yield by improving the quality of thesemiconductor fabrication, and also increase the productivity.

Semiconductor device manufacturing processing using the above-describedexposure apparatus will be explained. FIG. 15 shows the flow of thewhole manufacturing processing of the semiconductor device. In step S201(circuit design), a semiconductor device circuit is designed. In stepS202 (mask formation), a mask having the designed circuit pattern isformed. In step S203 (wafer manufacture), a wafer is manufactured by amaterial such as silicon.

In step S204 (wafer processing), called a pre-process, an actual circuitis formed on the wafer by lithography using a prepared mask and thewafer. Step S205 (assembly), called post-processing, is the step offorming a semiconductor chip using the wafer manufactured in step S204,and includes assembly processing (dicing and bonding) and packagingprocessing (chip encapsulation). In step S206 (inspection), inspectionssuch as the operation confirmation test and durability test of thesemiconductor device manufactured in step S205 are conducted. Afterthese steps, the semiconductor device is completed and shipped (stepS207).

For example, the pre-processing and post-processing are performed inseparate dedicated factories, and maintenance is done for each of thefactories by the above-described remote maintenance system. Informationfor production management and apparatus maintenance is communicatedbetween the pre-processing factory and the post-processing factory viathe Internet or dedicated network.

FIG. 16 shows the detailed flow of the wafer processing. In step S211(oxidation), the wafer surface is oxidized. In step S212 (CVD), aninsulating film is formed on the wafer surface. In step S213 (electrodeformation), an electrode is formed on the wafer by vapor deposition. Instep S214 (ion implantation), ions are implanted in the wafer. In stepS215 (resist processing), a photosensitive agent is applied to thewafer. In step S216 (exposure), the X-ray exposure apparatus describedabove exposes the wafer to the circuit pattern of a mask. In step S217(developing), the exposed wafer is developed. In step S218 (etching),the resist is etched except for the developed resist image. In step S219(resist removal), an unnecessary resist after etching is removed.

These steps are repeated to form multiple circuit patterns on the wafer.

As has been described above, the present invention can provide alignmentmarks which can be shared by global alignment and pre-alignment, andapplied to narrow scribe lines, and an alignment apparatus and methodusing the marks.

According to the present invention, global alignment and pre-alignmentare performed without switching the optical path by sharing an objectiveunit, thereby reducing an alignment time.

As many apparently widely different embodiments of the present inventioncan be made without departing from the spirit and scope thereof, it isto be understood that the invention is not limited to the specificembodiments thereof except as defined in the claims.

1. An exposure apparatus for exposing a substrate having an alignmentmark to light, said apparatus comprising: a first scope configured todetect a first image of the alignment mark on the substrate at a firstmagnification, the alignment mark comprising a first mark usable forboth coarse alignment measurement in a first direction and finealignment measurement in the first direction, and a second mark usablefor coarse alignment measurement in a second direction different fromthe first direction; a second scope configured to detect a second imageof the alignment mark on the substrate at a second magnification higherthan the first magnification; a processor configured to obtain a firstposition of the first mark in the first direction and a second positionof the second mark in the second direction based on the first image, andto obtain a third position of the first mark in the first directionbased on the second image; a stage configured to hold the substrate andto move; and a controller configured to control a position of said stagefor said second scope to detect the second image based on the obtainedfirst and second positions, and to control a position of said stage toexpose the substrate to light based on the obtained third position. 2.An apparatus according to claim 1, wherein each of said first and secondscopes comprises an image sensor, and said processor performs imageprocessing to obtain the first to third positions.
 3. An apparatusaccording to claim 1, wherein said first and second scopes comprise acommon objective optical unit.
 4. An apparatus according to claim 1,further comprising an illumination light source, common to said firstand second scopes, configured to illuminate the alignment mark.
 5. Amethod of manufacturing a device, said method comprising steps of:exposing a substrate having an alignment mark to light using an exposureapparatus as defined in claim 1; developing the exposed substrate; andprocessing the developed substrate to manufacture the device.
 6. Anexposure method of exposing a substrate having an alignment mark tolight, said method comprising steps of: detecting a first image of thealignment mark on the substrate using a first scope at a firstmagnification, the alignment mark comprising a first mark usable forboth coarse alignment measurement in a first direction and finealignment measurement in the first direction, and a second mark usablefor coarse alignment measurement in a second direction different fromthe first direction; detecting a second image of the alignment mark onthe substrate using a second scope at a second magnification higher thanthe first magnification; obtaining, using a processor, a first positionof the first mark in the first direction and a second position of thesecond mark in the second direction based on the first image;controlling, using a controller, a position of a stage, configured tohold the substrate and to move, for the second scope to detect thesecond image based on the obtained first and second positions;obtaining, using the processor, a third position of the first mark inthe first direction based on the second image; and controlling, usingthe controller, a position of the stage to expose the substrate to lightbased on the obtained third position.